What is in this article?:
- Integrated pest management has reduced pesticide applications in Arizona cotton from an 11.5 spray average per season for all pests in the early to mid 1990s to a 1.5 spray average today.
- Adjuvants are added to a spray tank to improve the physical characteristics of the spray mixture and/or to modify the action of an applied agrichemical.
- It is important to keep irrigation canal banks free of the invasive saltcedar to reduce fire risks near maturing wheat fields, alfalfa hay stacks, equipment storage areas, and orchards.
UA weed biologist Ed Northam discussed saltcedar, Tamarisk spp., an invasive plant found in riparian areas and irrigated cropping areas in the California and Arizona low desert regions.
Saltcedar grows as a bush or tree up to 18-feet tall in areas under 2,500 feet elevation, including along the Colorado River. Each saltcedar plant can produce thousands of flowers which become tiny seeds inside a single small capsule. Mature capsules are easily transported by wind.
The saltcedar was introduced to Arizona farms and ranches in the 1890s for stream bank erosion control and homestead windbreaks. Yet the lesson later learned was this weed aggressively colonizes in wet areas.
Dense populations consume large amounts of water. This requirement reduces available water for native plants in riparian areas and for irrigated agricultural fields near saltcedar-infested waterways.
Saltcedar seed can blow into wet areas in irrigated fields and invade canal areas; particularly those with dirt bottoms. Seedling stage to viable seed production occurs in several months when growing on a wet canal bank.
“Saltcedar is found in fallowed farm fields,” Northam said. “Saltcedar should be removed by cultivation before planting the next crop so the saltcedar root systems don’t mature enough to survive the plowing.”
Saltcedar roots can easily reach more than 20 feet below the soil surface. The deep roots draw naturally-occurring salt to the plant’s leaves where salty water literally drips onto the soil.
Additional salt in the upper few inches of the soil hinders native plant growth in non-cultivated areas and inhibits crop development where saltcedar has been cleared. In addition, saltcedar located on field edges can extend its root growth into the field and disrupt crop development.
Northam encourages farmers to keep field edges and canal banks clear of saltcedar since once it matures the plants become seed sources for new infestations.
“Remove saltcedar when the plant is young,” Northam said. “Seed can also fall or blow into the irrigation water. Flowing natural or irrigation water delivers seed downstream providing opportunities for new plants to establish further away.”
Saltcedar along a canal also serves as a conduit for destructive fire especially around maturing wheat fields, alfalfa hay stacks, equipment storage areas, and orchards.
A weed wrench hand tool can be used to pull young saltcedar plants from the soil. Plants with fewer than eight to 10 stems and main root diameters less than 4 inches can be removed with the weed wrench in moist soil. For larger plants, mechanical remedies include bulldozers, single-tree excavators, and mulchers.
Foliar herbicides with the active ingredients imazapyr, glyphosate, and triclopyr can provide effective saltcedar control, Northam says.